pulse_mixer: protect the struct with a mutex

There are numerous race conditions between the libpulse thread
(pulse_mixer.c callbacks) and the rest of MPD.  Protect the volatile
attributes of the pulse_mixer struct with a mutex to fix that.

1 files changed, 29 insertions, 1 deletions

diff --git a/src/mixer/pulse_mixer.c b/src/mixer/pulse_mixer.c
index 1f077e2b7..b6ea077f1 100644
--- a/src/mixer/pulse_mixer.c
+++ b/src/mixer/pulse_mixer.c
@@ -36,6 +36,8 @@ struct pulse_mixer {
 	const char *sink;
 	const char *output_name;
 
+	GMutex *mutex;
+
 	uint32_t index;
 	bool online;
 
@@ -95,9 +97,13 @@ sink_input_cb(G_GNUC_UNUSED pa_context *context, const pa_sink_input_info *i,
 	g_debug("sink input cb %s, index %d ",i->name,i->index);
 
 	if (strcmp(i->name,pm->output_name) == 0) {
+		g_mutex_lock(pm->mutex);
+
 		pm->index = i->index;
 		pm->online = true;
 		pm->volume = i->volume;
+
+		g_mutex_unlock(pm->mutex);
 	} else
 		g_debug("bad name");
 }
@@ -120,7 +126,10 @@ sink_input_vol(G_GNUC_UNUSED pa_context *context, const pa_sink_input_info *i,
 	}
 
 	g_debug("sink input vol %s, index %d ", i->name, i->index);
+
+	g_mutex_lock(pm->mutex);
 	pm->volume = i->volume;
+	g_mutex_unlock(pm->mutex);
 
 	pa_threaded_mainloop_signal(pm->mainloop, 0);
 }
@@ -136,6 +145,8 @@ subscribe_cb(pa_context *c, pa_subscription_event_type_t t,
 
 	switch (t & PA_SUBSCRIPTION_EVENT_FACILITY_MASK) {
 	case PA_SUBSCRIPTION_EVENT_SINK_INPUT:
+		g_mutex_lock(pm->mutex);
+
 		if ((t & PA_SUBSCRIPTION_EVENT_TYPE_MASK) ==
 		    PA_SUBSCRIPTION_EVENT_REMOVE &&
 		    pm->index == idx)
@@ -146,12 +157,15 @@ subscribe_cb(pa_context *c, pa_subscription_event_type_t t,
 			o = pa_context_get_sink_input_info(c, idx,
 							   sink_input_cb, pm);
 			if (o == NULL) {
+				g_mutex_unlock(pm->mutex);
 				g_debug("pa_context_get_sink_input_info() failed");
 				return;
 			}
 
 			pa_operation_unref(o);
 		}
+
+		g_mutex_unlock(pm->mutex);
 		break;
 	}
 }
@@ -215,6 +229,8 @@ pulse_mixer_init(const struct config_param *param)
 	pm->sink = config_get_block_string(param, "sink", NULL);
 	pm->output_name = config_get_block_string(param, "name", NULL);
 
+	pm->mutex = g_mutex_new();
+
 	return &pm->base;
 }
 
@@ -223,6 +239,7 @@ pulse_mixer_finish(struct mixer *data)
 {
 	struct pulse_mixer *pm = (struct pulse_mixer *) data;
 
+	g_mutex_free(pm->mutex);
 	g_free(pm);
 }
 
@@ -314,12 +331,15 @@ pulse_mixer_get_volume(struct mixer *mixer)
 	int ret;
 	pa_operation *o;
 
+	g_mutex_lock(pm->mutex);
 	if (!pm->online) {
+		g_mutex_unlock(pm->mutex);
 		return false;
 	}
 
 	o = pa_context_get_sink_input_info(pm->context, pm->index,
 					   sink_input_vol, pm);
+	g_mutex_unlock(pm->mutex);
 	if (o == NULL) {
 		g_debug("pa_context_get_sink_input_info() failed");
 		return false;
@@ -328,7 +348,12 @@ pulse_mixer_get_volume(struct mixer *mixer)
 	if (!pulse_wait_for_operation(pm->mainloop, o))
 		return false;
 
-	ret = (int)((100*(pa_cvolume_avg(&pm->volume)+1))/PA_VOLUME_NORM);
+	g_mutex_lock(pm->mutex);
+	ret = pm->online
+		? (int)((100*(pa_cvolume_avg(&pm->volume)+1))/PA_VOLUME_NORM)
+		: -1;
+	g_mutex_unlock(pm->mutex);
+
 	return ret;
 }
 
@@ -339,7 +364,9 @@ pulse_mixer_set_volume(struct mixer *mixer, unsigned volume)
 	struct pa_cvolume cvolume;
 	pa_operation *o;
 
+	g_mutex_lock(pm->mutex);
 	if (!pm->online) {
+		g_mutex_unlock(pm->mutex);
 		return false;
 	}
 
@@ -348,6 +375,7 @@ pulse_mixer_set_volume(struct mixer *mixer, unsigned volume)
 
 	o = pa_context_set_sink_input_volume(pm->context, pm->index,
 					     &cvolume, NULL, NULL);
+	g_mutex_unlock(pm->mutex);
 	if (o == NULL) {
 		g_debug("pa_context_set_sink_input_volume() failed");
 		return false;